When viscous magma, containing much gas, is erupted under reasonably low pressure, a glowing cloud containing ash and pumice may be thrown into the air, this cloud will fall back onto the earth like an avalanche before it can cool off.  This avalanche is called a nuée ardente.

     Nuées ardentes were discovered during the eruption of Mount Pelée in 1902.  They are often the biggest killers in the volcanic repertoire.  The direct translation of nuée ardente is "incandescent cloud", however "glowing avalanche" is perhaps a better description.

     Nuées ardentes contain mixtures of gas, lava, blocks, ash and pumice.  They move very fast reaching speeds ranging to 500km an hour.  The paths that they take are influenced by gravity.  Because they often strike the ground many people are killed.

     Nuées ardentes are common features during Pelean and Plinian eruptions.

(Fig. 2.36) In this situation the craterpipe is blocked by a lava-stopple.  Pressure under the stopple increases until a weak spot is found.  At Mount Pelée this weak spot was a fissure on the side of the crater.  The result is a lateral nuée ardente.